Field of the Invention
The present invention relates to a sheet processing apparatus and a method for controlling a sheet processing apparatus.
Description of the Related Art
Conventionally, there has been a sheet processing apparatus that executes punching processing on a sheet on which an image is formed by an image forming apparatus. Such a sheet processing apparatus can punch a different number of holes in the sheet, e.g., two holes, three holes, or thirty holes.
On the other hand, pre-punched sheets, in which holes are pre-punched for filing, have been known.
Execution of punching processing on a pre-punched sheet enlarges pre-punched holes of the sheet to cause the position of the sheet to become unstable when the sheet is filed.
In order to solve this problem, there has been discussed a technique in which the number of punch holes of a pre-punched sheet is registered in advance as sheet information and no punching processing is executed if a sheet fed from a sheet feeding tray is determined to have pre-punched holes (refer to Japanese Patent Application Laid-Open No. 2001-316036).
This conventional technique can execute punching processing on a sheet other than a pre-punched sheet while executing no punching processing on a pre-punched sheet, and can then discharge the sheets to a single sheet discharging tray.
However, the user might set the number of holes to be punched by the punching processing that is different from the number of holes that are pre-punched in a pre-punched sheet. In this case, the number of punch holes punched in a sheet other than a pre-punched sheet is not the same as the number of holes punched in a pre-punched sheet. Thus, the positions of the holes in the sheet other than the pre-punched sheet do not coincide with the positions of the holes in the pre-punched sheet. As a result, a hole of a sheet is covered with another sheet when the sheets are bundled. Therefore, it is impossible to file the sheets.